To bromo enol ether 2 (4 mmol) in 10 ml of THF was added t-BuLi (1.7M in pentane, 10 mmol, T<−65°C) under argon. After 45 min at −70°C, ClSiMe 3 (0.43g, 4 mmol) was added. The mixture was kept at −70°C (50 min) then warmed to 0°C in 10 min, then treated with 5% Na 2